The present invention relates to a cooling device for liquid crystal projectors, and more particularly to an optical system utilized to cool a liquid crystal projector.
The liquid crystal projector is one product presently being actively developed. The structure of the penetration type liquid crystal projector is shown in FIG. 1. White light (consisting of red, green and blue light) first passes through LA (lens array A), then is bended at MR1 (Mirror 1; first reflecting mirror), then it passes through LB, a polarizer (PSC) and a condenser lens (CD1). DM1 (first dichroic mirror) will let blue light penetrate through it, while reflecting green and red light. At that time, the blue light will bend at MR2, pass through a linear polarizer, and be modulated through a blue-light LCD panel. After passing through a light-examining polarizer, it enters into the first face of a cross dichroic prism (XP). When the green and red light passes through DM2, DM2 will reflect the green light and cause it to pass through a linear polarizer and enter a green-light LCD panel (LCg) to be modulated. It then passes through a light examining polarizer, and enters the second face of the cross dichroic prism (XP). The red light penetrates DM2, MR3 and MR4, then passes through the linear polarizer and enters a red-light LCD (LCr) to be modulated. After passing through the light-examining polarizer, it enters the third face of the cross dichroic prism (XP). After the three colors of light have entered the cross dichroic prism to be synthesized, the synthesized light passes through the fourth face of the cross dichroic prism and enters the projection lens (PL), so as to project the image on to a screen (S).
Generally speaking, in the LC projector, because light is emitted by gas discharge, the high-temperature light being emitted is collected and projected onto the LC panel to cover the light-examining polarizer of the cross dichroic prism, causing the temperature of the LC panel and light-examining polarizer to increase. So, when the LC projector is being operated, the LC panel and light-examining polarizer must be cooled properly in order to allow the LC panel be able to show clear images on the screen, and not to lose the function of light modulation. Meanwhile, the light-examining polarizer is not to be burned down. The cooling devices currently in effect are air-cooling and fluid cooling.
1. Air cooling: three cooling holes, which correspond to the three LC panels respectively, are opened on the base plate, upon which the cross dichroic prism is fixed, and a cooling fan is installed below the base plate. The air current generated from the cooling fan is directed to the illumination area of the LC panels, to increase the temperature of the air current after it flows past the LC panels, removing the heat of the LC panels. However, such a cooling method cannot increase cooling efficiency if the speed of the air current is increased after it has reached a critical value. Moreover, at the present stage of development, the illumination of the projector is being largely increased while the dimensions of the panel are being decreased, thus causing cooling tunnels and cooling areas to become decreased. Therefore, the cooling requirements of the LC panels are already beyond of the limits of air-cooling.
2. Fluid cooling: the following fluid cooling manner is developed on account that the air cooling has its own limit: the fluid cooling manner, as disclosed in U.S. Pat. No. 4,772,098, is to add a penetration type cooling container and heating tubing device, penetration type coolant is received in the inner part of the penetration type cooling container, and the one surface of the outer part is stuck to one surface of the LC panel, also, the heating tubing device has an absorber inserted in the penetration, type cooling container and a radiator installed at the outer part of the penetration type cooling container utilized to carry away the heat absorbed by the absorber so that the temperature of the LC panel can be lowered. But only one face of the LC panel is installed on the penetration typecooling container in this patent so that the heat at another face of the LC panel cannot be carried away. Furthermore, LC projector become smaller and smaller at the present time, the device provided in this patent is gradually unable to dissipate the heat fast and effectively; and also unable to cool the light-examining polarizer properly.
U.S. Pat. No. 5,170,195 discloses a fluid-cooling manner, which is to add a shielded container, convection strengthening device and cooling fins in a LC projector. The shielded container can let light penetrate and coolant is filled therein, a light examining polarizer and LC panel are disposed at the front and rear walls of the shielded container respectively, and the convection strengthening device is to utilize fluid to carry the heat of the light examining polarizer and LC panel away to the surroundings of the container, then utilize cooling fins disposed around the surroundings of the container to carry the heat of fluid away from the container so as to lower the temperature of the light examining polarizer and LC panel. But, the container disclosed in this patent is only positioned at one side of the light examining polarizer and LC panel, therefore, it is no way to carry the heat away from another side of the light examining polarizer and LC panel. At the present that LC projector is miniaturized, this patent still has no fast and effective way to dissipate the heat.
Again, U.S. Pat. No. 5,767,924 discloses another fluid-cooling manner, which is to add a container, which coolant is stored therein, in the LC projector, and to immerse the LC panel in the way of the light path into the inner part of the container so as to lower the temperature of the LC panel. But, because the temperature of LC panel is lowered only by increasing the temperature of the coolant, and without any other elements to carry away the increased heat of the coolant, therefore, this patent has no effective way lowering the temperature of the LC panel like the above-mentioned patents.
The main object of the present invention is to provide a cooling device, utilized to cool a LC panel and polarizer of an optical system effectively.
According to the cooling of the LC projector disclosed by the present invention, it comprised a optical system, flow guiding system, heat dissipation system and container, and mainly locates the optical system, current guiding system and heat dissipation system in the container that is full of transmitting coolant. When the optical system is exposed to the light and heated, the coolant will carry the heat of the optical system away, and the flow guiding system is utilized to guide the coolant to flow in order to lead low temperature fluid to the optical system and the high temperature fluid to the heat dissipation system to be cooled, and then the heat absorbed by fluid is dissipated out of the container through the heat dissipation system.